1. Field of the Invention
This invention relates to a supporting pillar of the type called a "travelling support." More particularly, this invention relates to a supporting pillar which is intended for use in underground mines.
It is known that a travelling supporting pillar usually includes a sole plate that is intended to bear against the floor, and a top that is intended to be applied against the roof, with hydraulic jacks acting as stanchions inserted between the sole plate and the top. In some pillars, a gate or a shield is inserted between the sole plate and the top with the end of the shield joined to the top to protect the rear of the pillar against rock falls that may be caused by cave-ins or fill-ups.
2. Description of the Prior Art
French Pat. No. 2,263,370 describes a pillar including a gate where a pivoting lever 6 is inserted between the end 7 of the gate 2 and the top 5 such that a jack 9 can move whenever it is not hard against the roof. This enables the top 5 to be positioned very close to the working face 22 before sending the load into the stanchions 4 that support the pillar against the roof. This prior art device is intended to correct the articulation movements which are characteristic of pillars that are equipped with a gate at times when the pillar is not tightened against the roof. In fact, when the gate in such a prior art pillar is joined directly to the rear of the sole plate, its forward end tends to describe an arc of a circle, and this will usually result in an increased distance between the top 5 and the working face, especially when the thickness of the seam is greater. The presence of the hinged lever 6 and its jack 9 allows correction for this effect, and for conveniently locating the top 5 with reference to the working face 22, before the tightening of the pillar against the roof. However, after the tightening of the pillar to the roof, the lever 6 remains positively locked on the gate 2, by an undeformable mechanism (notched sector 30, pin 31, eyelet 32, locking hole 33). In other words, the object of the device described in French Pat. No. 2,263,370 is to prevent any relative displacement of the top 5 with reference to the gate 2, other than a pivoting about the axis 8.
However, the aforesaid prior art device has certain disadvantages:
the supporting pillar may have a considerable height and length, which makes it difficult to transport the pillar to the bottom of the mine, requiring, consequently, a great amount of time for installation in the mine; and
the supporting pillars that are pressed against the top are often subjected by the relative movements of the walls, to stresses whose direction does not always correspond to the sliding direction of the pillar, resulting in the development of substantial stress components directed forwards or backwards of the support, and these can cause slippage of the top on the roof or of the sole plate on the floor. As a result, the loads on the frame of the pillar, especially the rear links, are often substantial. These forwardly and backwardly directed stresses of the pillar can also appear during the tightening of the pillar if the sole plate is not on a stable support, and this can result in damage to the pillar or an inadequate support.